In contrast to conventional offset printing in which the work is done with a moistening agent, in anaqueous offset printing a special silicone layer keeps the nonprinting places of the printing form free of ink. This property of the silicone surface collapses above a certain temperature, which is about 35.degree. C. The optimal operating temperature is 25.degree. C. or below.
From the journal "Offsetpraxis" 4/1990, pages 38 to 46, it is known, as an alternative to an inking mechanism roller tempering, in which as cooling medium a fluid is used, in anaqueous offset printing to blast the printing form laid about the printing form cylinder with cold air at a certain angle so that the printing form temperature can be maintained constant at the above-mentioned operating temperature. In such offset printing presses a blast box installed instead of the conventional moistening roller system distributes the cold air onto the printing form over the whole width of the printing form cylinder. For this purpose the blast box is connected with a thick air feed tube which transports cold air from a cooling installation set up beside the printing press to the printing form cylinder of the printing mechanism. In such printing form cylinder cooling, not only is the appearance of the printing press disturbed by the thick long air feed tubes that must be assembled, but also the accessibility to the printing mechanisms is hampered.
In connection with the blasting of the printing form by means of cold air, tempering is also a concern, because besides cooling there also occurs a warming until the surface of the printing form, in the case of a cold printing press, is brought to the optimal operating temperature of, for example, 25.degree. C. The need therefor exists for a thermal regulator for the printing form. Moreover, it is a problem to create a thermal regulator for a printing form laid about a printing form cylinder for anaqueous offset printing, which makes it possible to blast the printing form by means of tempered air which is generated directly in the zone of the printing form cylinder. The present invention is directed to a solution to these problems.